The present invention relates to grinding and polishing pads and, in particular, to grinding and polishing pads used in conjunction with lens lapping tools for grinding and polishing optical and ophthalmic lenses. More specifically, the present invention relates to an improvement in the means by which ophthalmic lens surfacing pads are attached to lens lapping tools.
Optical and ophthalmic lenses are generally made by generating a lens blank to the desired curvature on a curve generator and then lapping the lens by means of an abrasive slurry and an oscillating lapping tool. Lapping tools are usually cast iron or aluminum tools having various lapping surfaces, each of a curvature corresponding to a desired lens curvature. Thus, an optical manufacturer requires a set of lapping tools in order to manufacture lenses of various prescriptions.
Lapping pads which conform exactly to the lapping tool curvature are generally used on the surface of each lapping tool. Lapping pads, sometimes referred to as surfacing pads, usually wear relatively quickly and are replaced after several lenses are ground. But lapping pads provide a relatively inexpensive surface which will wear instead of the relatively expensive lapping tool.
Recently, improved lapping pads have been developed which contain lapping abrasive on the surface of the pad or impregnated into it. One lapping procedure using such pads involves adhesively attaching a first fining sandpaper pad to a lapping tool and fine grinding a lens under running water to the proper curve. Then, a second fining pad of smaller grit than the first pad is placed over and adhered to the first pad and the lens is subjected to a second fining step under running water. Next, both pads are removed from the lapping tool, a flocked polishing pad is adhered to the tool and the lens is polished to a clear finish under a polishing slurry.
The aforementioned lapping procedure can be used for glass and plastic lenses. However, the procedure has certain disadvantages. An operator must frequently attach and remove the pads of which are adhesively secured either to the surface of the lapping tool or to a pad on the surface of the tool and can be difficult to peel off the tool. Furthermore, the pads can be difficult to attach to the tools without wrinkles, which adversely effect the performance of the pad. Coolant water flowing over the pads serves to further increase the difficulties encountered in attaching and removing the pads. The present invention provides an improved lens surfacing pad and method which reduces these difficulties. Further understanding of this invention will be had from the following description and accompanying drawings.